This invention relates to refrigerant compressor units of a type in which the reciprocating movement of pistons within cylinders is caused by the nutation of a non-rotatably but nutatably supported wobble plate driven by a cam rotor, and, in particular, to improvements of the wobble plate itself.
Such refrigerant compressor units have been known and advantageously used for compressors in air-conditioning systems for automobiles, because of the their compactness and lightness.
In the refrigerant compressor unit, because the wobble plate is connected to respective pistons by piston rods, the rotation of the wobble plate must be prevented to assure smooth nutation. To this end, the wobble plate has a bevel gear which engages with a mating bevel gear non-rotatably supported on the cylinder block. The wobble plate is supported on the inclined surface of the cam rotor through a needle thrust bearing and is born on a ball bearing seated in ball seats formed in the bevel gears. Thus, the wobble plate nutates about the center of the ball bearing upon the rotation of the cam rotor, and is prevented from rotating by the engagement between the bevel gears.
In a known construction of the wobble plate, the wobble plate 1 comprises a plate member 2 and a bevel gear member 3, as shown in FIGS. 2a-2c. Bevel gear member 3 is provided with an annular flange 4 on the peripheral side surface and with an axial rectangular boss 5 on the backside. Plate member 2 is provided with a depression 6 for receiving bevel gear member 3. In the bottom of the depression, a rectangular hole 7 is formed for receiving rectangular boss 5. The wobble plate is completed by fitting bevel gear member 3 into depression 6 of plate member 2 with boss 5 being inserted into the hole 7, followed by caulking the radial edge of the depression 6 over annular flange 4, as shown by reference numeral 8. Thus, bevel gear member 3 is secured to plate member 2 to prevent relative axial movement, while relative rotation of the plate member and the bevel gear member is prevented by fitting the boss into the hole.
Plate member 2 is also provided with a plurality of equiangularly spaced ball sockets 9 for receiving end balls of piston rods.
In the known construction, production of the wobble plate is difficult, because the wobbling center is off from the center axis of the wobble plate if hole 7 is not accurately formed at the center of plate member 1.
Furthermore, since relative rotation is prevented near the center of the wobble plate, great strength in preventing relative rotation is not achieved. If the thickness and the length of boss 5 are increased with the thickness of the bottom plate also being increased, strength is increased by on increase in weight of the wobble plate results.